Changes between Version 16 and Version 17 of u/NewUsers


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Timestamp:
09/06/11 12:08:34 (13 years ago)
Author:
Erica Kaminski
Comment:

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  • u/NewUsers

    v16 v17  
    1212== Forming Sinks ==
    1313
     14The first step in forming a sink particle is -- a cell somewhere in the grid must exceed the density threshold given by the code. Currently, Astrobear implements a density threshold that is the [SinkParticles Truelove criterion].
     15
     16So say you have a situation like that drawn below:
     17
    1418[[Image(page1.png, 25%)]]
    1519[[Image(page2.png, 25%)]]
     20
     21Astrobear then progresses through the checking for new sink particles routine, located in the particle directory in the file called {{{particle_info_ops.f90}}}. The subroutine is called '''!CheckForNewParticle(Info)'''. Essentially, this subroutine goes through a series of checks that ensures the conditions are suitable for sink particle formation. After the grid has been swept and a cell has been detected that violates the Truelove criteria then a control region, 4 cells in radius centered on the zone in question, is evaluated for the following:
     22
     23* Is this flow converging?
     24* Is this cell a potential minima within a radius of 4dx?
     25* Is the surrounding region Jean's unstable?
     26* Is this region gravitationally bound?
     27* Is this cell within a small enough proximity to an already formed sink?
     28
     29A sink will form only if all of these conditions are satisfied.
     30
     31Now, sometimes insufficient resolution can impede the formation of sinks. If you have a zone that has exceeded the density threshold, you may work through some algebra to show the size of dx that is required for collapse (I have attached some scratch notes on this to the bottom of this page for example). Also, there are a series of print statements in the subroutine mentioned above that you can uncomment. This will show you what has passed and what has not.
     32
     33The sink routines are more or less taken from [http://adsabs.harvard.edu/abs/2010ApJ...713..269F Federrath et al]. I have added a summary of this paper and its findings on my page, under the library section.
    1634
    1735== Effectively Implementing AMR ==